Characteristic features always holds true for the corresponding group of animals

Which of the following characteristic features always holds true for the corresponding group of animals?
(1) 3-chambered heart with one incompletely divided ventricle – Reptilia
(2) Cartilaginous endoskeleton – Chondrichthyes
(3) Viviparous – Mammalia
(d) Possess a mouth with an upper and a lower jaw – Chordata